1. Field of the Invention
The invention pertains to a spoiler for an aerodynamic body of an aircraft with an aerodynamically active surface, particularly for an airfoil of an aircraft, wherein said spoiler is supported on the aerodynamic body such that it is articulated about an axis extending transverse to the air flow direction and can be adjusted relative to the air flow.
2. The Prior Art
In the most general sense, spoilers are surfaces provided on aerodynamically active surfaces of aircraft which can be adjusted relative to the air flowing along the surface in order to fulfill their function. The most widely used spoilers are provided on the upper side of the airfoil of an aircraft, namely in the rear region thereof, and used for lift dumping, as well as for increasing the lift and for roll control purposes in cooperation with a high-lift surface arranged behind the main wing. Lift dumping is realized, for example, at the end of a landing maneuver by adjusting the spoilers that are supported such that they are articulated about an axis extending transverse to the air flow direction upward relative to the air flow, wherein this upward adjustment leads to an abrupt separation of the flow at this location of the air flow profile and therefore to a massive lift reduction. On the other hand, spoilers may also be used for increasing the lift, particularly within the range of small angles of attack (zero-lift), wherein the spoilers are lowered and adjusted relative to an air flow while the high-lift surfaces are extended, and wherein said air flow flows from the underside of the main wing to the upper side of the high lift surface through a gap between the high-lift surface and the main wing that is exposed when the high-lift surface is extended.
In order to improve the lift within the range of the aforementioned small angles of attack, it is currently common practice to essentially utilize double-gap or multi-gap flaps, namely so-called Fixed Vane flaps or MCS (Multi Control Surface) components. The aerodynamic effectiveness of these systems is associated with greatly increased complexity with respect to the structure and the system architecture, as well as with significant additional weights. However, additional weight basically impairs the cruising performance and the additional system components and the increased complexity result in higher manufacturing, operating and maintenance costs.
A conventional spoiler is typically formed by a spoiler surface that is supported by means of an articulation such that it can be pivoted about an axis that essentially extends transverse to the air flow direction, i.e., essentially in the wingspan direction of the airfoil, as illustrated in the form of a cross section in FIG. 1. This figure shows an airfoil, in which the spoiler 5 is supported in a pivoted fashion on the upper rear side of the main wing 1 by means of a spoiler articulation 11. A high-lift surface 4 is illustrated in the extended state such that a gap 16 is exposed, through which the air flows from the underside of the main wing 1 to the upper side of the high-lift surface (landing flap) 4. The excursion of the spoiler 5 therefore takes place in the form of a rotational movement about the articulation 11 such that the spacing between the rear edge of the spoiler 5 and the upper side of the high-lift surface 4 is reduced and the air flow is accelerated at this location in order to increase the lift accordingly. When the spoiler 5 is lowered in order to increase the wing curvature, the articulation line on the articulation 11 acts as an aerodynamic limitation because the flow is no longer able to follow the discontinuous wing surface at this location and therefore separates.
The basic function of a spoiler is suitable for three applications:
a) In the simplest instance of a roll control function, the gap is closed and the spoiler acts like a split flap at small excursions. In simple terms, such a split flap deflects the flow behind the wing in the direction of excursion and therefore generates a “lifting” force opposite to the direction of excursion. It appears as if the rear edge of the wing is virtually displaced analogous to a normal pivoted flap. The drag increases due to the eddying of the separated flow on the “inner side” of the opened spoiler, wherein this increased drag is only partially desirable as a secondary effect in this case. A wing that moves upward as the lift increases due to an aileron excursion usually has a tendency to lag and the side being lowered has a tendency to lead. The additional drag of the spoiler counteracts this tendency to lead. At a symmetric excursion on both wing sides, the gliding angle can be influenced without excessively increasing the drag during the descent from the cruising altitude.b) Both effects are also utilized in the equally simple instance of the lift dumping function (primarily at full excursion during the roll-out on the ground after landing): the loss of lift and the significant deceleration effect resulting from the separated flow on the inner side of the spoiler and the upper side of the high-lift system. The “accumulation” on the front side of the spoiler also has a deceleration effect. It is attempted to keep the aircraft on the ground (lift reduction) and naturally also to bring the aircraft to a standstill (deceleration effect).c) It is attempted to increase the lift in slow flight during takeoff/landing maneuvers. Two effects can be achieved with the spoiler in this case: “influencing the effective curvature of the overall system” and “optimal design of the gap between the participating high-lift elements” (in this case spoiler/flap).